The effect of different natural enemies on the performance of Cirsium arvense in its native range

Understanding the effects of herbivores on weedy plant performance under different habitat conditions may provide useful information for limiting the spread of these plant species in their native and invaded ranges. A critical drawback to using herbivores to limit the spread of weedy plant species is the limited knowledge regarding the effects of different natural enemies on plant performance under natural conditions and in different habitat types. The aim of this study was to collect information on the degree and types of damage caused by natural enemies and their effects on the performance of the weed species Cirsium arvense, under different abiotic conditions in its native range in the Czech Republic. Damage induced by different natural enemies of C. arvense in four different populations in wet and dry sites was studied. The most common types of damage found in C. arvense were folivory (eaten foliage), external stem damage and leaf necrosis, and their occurrence varied strongly in space and time. Different plant damage types tended to be significantly associated with each other. It was therefore difficult to separate the effects of individual damage types and to study their interactions. Overall, the results indicate that in its native range, C. arvense experiences high levels of herbivory, with stem damage, flower herbivory and folivory having the strongest effects on plant performance. Experimental studies that would separate the effect of single herbivores are, however, needed to confirm this.